1. Field of the Invention
This invention relates to angular accelerometers and more particularly to a type of device which operates on a principle whereby the relative motion between a gas or fluid volume (inertial mass) contained within an annulus or torroid is sensed by means of measuring the heat transfer between thermally sensitive elements located within the fluid volume and fixed in position to the container.
2. Description of the Prior Art.
The operation of all common types of linear or angular accelerometers is based on Newton's Second Law of Motion: Force=Mass.times.Acceleration (F=MA). A force on a mass is proportional to the amount of acceleration to which the mass is subjected. As the force on a mass is measured, the amount of acceleration can be determined. Common types of accelerometers known to prior art include:
(1) Potentiometric: An applied acceleration moves a sensitive mass which is a sliding contact of a resistive element. PA0 (2) Strain Gauge Type: An acceleration sensitive mass is mounted to a wire which changes resistance in proportion to the applied forces. The resistance is usually determined using a Wheatstone Bridge Circuit. PA0 (3) Piezo-Electric: A piezo-electric crystal produces an electrical output proportional to an applied force (acceleration). PA0 (4) Variable Reluctance: The reluctance of a magnetic path is varied by an acceleration sensitive moving armature producing an output proportional to applied acceleration. PA0 (5) Servo Accelerometers: An acceleration sensitive mass (liquid or solid), when subjected to a force, causes a position error signal to be generated, which through servo action, or feedback, force restores the mass to its original position. The feedback required is proportional to the applied force, i.e. acceleration.
The disadvantages of these types of accelerometers in addition to being difficult to manufacture and thus relatively costly are their limited frequency response, poor cross-axis sensitivity, and poor temperature sensitivity characteristics. In addition, their reliance on mechanical couplings and their connections to an acceleration sensitive seismic mass generates peculiarities to each type which effect the device performance characteristics, such as linearity, hysteresis, repeatability, phase angle, null offset and null uncertainty because of mechanical variations and wear due to random vibration and normal useage.